Bradykinin-induced atropine-sensitive gastric contractions. Activation of an intramural axon reflex?

Gastric motor responses, recorded as volume changes of an intragastric balloon, were induced by the close i.a. administration of bradykinin (0.75-4 micrograms) in chloralose-anaesthetized cats. The animals were vagotomized and the adrenals were ligated at the outset of the experiments. Prior to autonomic blocking agents bradykinin elicited relaxatory or biphasic motor responses. Following nicotinic ganglionic receptor blockade bradykinin caused predominantly gastric contractions. Such excitatory responses were antagonized by 80-100% by atropine, suggesting a dominant neurogenic component. An hypothesis is put forward that the observed gastric contractions result from a bradykinin-induced activation of an axon reflex arrangement confined to thin sensory nerve fibres which, by substance P release from intramural collaterals, excite postganglionic cholinergic motor neurones.